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Old 11-21-2011, 06:26 AM
  #45  
MTK
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Join Date: May 2004
Location: Whippany, NJ
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Default RE: OS 33GT Gasoline Engine for Pattern

ORIGINAL: choihjin

So far so good, after getting OS GT 33 taken 15 days delivery to Korea.
Breaking in with 18X10 Hawk wooden prop, gas/motul 800 (33:1) with Stock muffler gave 7500 RPM, followed by the manual, highest RPM on low speed needle then opened 90 degree, highest RPM (7800) on high speed needle then 30 degree open.
Just 2 liters through on the GT33, it gave very reliable speed up without any hesitation. Many mentioned, throtle response is nearly linear.
Manual suggests to use electric starter, but due to too much torgue it failed to turn with electric starter. By hand start without enough speed, the engine turns backward. Matt K mentioned already. But hand start on the middle part of the prop, not on the end tip of prop resulted positive forward engne start.
The sound and vibration are much softer than any other gasser, I experienced.
After removing DLE 30, mounted it on Rock&Roll with Cannister for DLE 30, RPM droped to 6800 RPM, but better than DLE 30 which gave 6500 RPM, but unstable. During engine running it suddenly stoped at high RPM or even fordward revolution turns into barkward. It is scary. Weather was colder 7 degree C (45 degree F).
After more precise needle setup, maiden flight was succesful. I believe, it will give better results after full break-in and less oil contents.
I am waiting Hyde mount which is known to reduce noisy and vibration, but also even giving more RPM and lowering engine exhaust temperatre, resulting in better engine efficiency.
I am waiting the Hyde mount for my Smaragd. I will post some photo and results.
Matt K, I hope you had a lemon not the design problem. If it is due to design problem, you are waisting too much time and efforts, me too.
Hope to hear good news from Tower.
Good Luck and Regards, MATT K.
Uh Oh.....That's not good news. I am sorry to hear similar issues as mine. That does not speak well for the engine design. I wish I had measured the timing on it. It sounds like it way too retarded and is the likely cause of all these problems

As I recall, the 140RX had carburetion issues when first released too. Their 200 4 stroke has crankshaft issues, I have heard. I am surprised because I have always had the impression that OS did considerable alpha testing before sending their product out to the market. YS on the other hand often used us modelers as beta testers. Well, so much for impressions. The reality is something different.

BTW- I also have a Mintor 38 in test right now. I don't have it piped yet. Can't seem to find a header for the 38. The exhaust flange would need an adapter so that available headers (Hatori or Karl Mueller) could be fitted. The Mintor, in direct contrast, is so easy to start and run it makes this chore simple. Too early to tell what the performance is like since I've only played with an 18x10 apc, getting respectable power. Will try to fit the engine into my EF EXtra over the Thankgiving holiday and get a few flights on it to see for real what it can do